Retrofit or New Build?

Andrew Leiper

Net Zero Carbon Leader and Principal Engineer

Max Fordham LLP

Hufton + Crow

Everyone reading this will occupy, operate or own an existing building or buildings.

Whichever is the case, it is more likely than not that your building will still be in use in 2050. In fact 80% of the buildings with us today will still be in use in 2050. The energy consumption of existing buildings accounts for around 34% of the UK’s annual carbon emissions and we all need to be considering ways of reducing the carbon footprint of our buildings.

Much attention is paid to new-build performance and, although challenging, we know how to construct new ultra-low energy “net zero carbon compatible” buildings. Net zero carbon compatible buildings are designed and built to minimise carbon emissions throughout their lifecycle. Organisations such as LETI and the RIBA (in their 2030 challenge) give detailed guidance on suitable targets for embodied carbon and energy use intensity of new buildings.

While we would encourage everyone thinking of commissioning a new building to include net zero carbon in their brief, the real elephant in the room is how to go about reducing carbon emissions from our existing building stock. The question for the custodians of existing buildings should not be whether to retrofit but how deep and how soon to retrofit!

“Retrofit” is a term you may have heard used with increased frequency over the last few years. A retrofit involves the installation of an element or technology into an existing building which wasn’t there previously. It’s commonly used to describe an upgrading of elements within a building, such as thermal insulation or replacement of the heating system technology to improve efficiency and reduce carbon emissions.

There are different drivers to retrofit, including:

  • An organisation’s or individual’s desire to reduce their carbon emissions
  • Improved comfort, health and wellbeing
  • Reduction in energy bills
  • A circular economy approach encouraging “retrofit first” and the reuse of an existing building rather than building new
  • ESG investing and Green finance is also becoming mainstream – mortgage rates are just one example where it will shortly be cheaper if your building is greener

What Is the Best Approach for My Building?

A significant proportion of the carbon emissions associated with buildings arise from the materials used and the construction process itself, these are the “embodied carbon emissions” of a building. Extending the lifespan of a sound existing building which is capable of adaption to meet an occupier’s future needs can be a lower carbon pathway than demolishing and building new. Undertaking a retrofit to maximise an existing buildings energy efficiency and decarbonise its sources of heat and electrical power will help ensure that the building can provide a comfortable environment and low energy performance well into the future. The embodied carbon associated with the construction of a typical new building can be equivalent to 20 years worth of its operational carbon emissions, in the future as our new buildings tend towards ultra low operational energy consumption, then this could conceivably stretch to 40 years. Over the timeframe of 10-30 years (depending on the particular deadline for net zero) then it is likely that retrofitting existing buildings, where possible, will have a more positive impact on climate change than building new.

As a Building Owner or Operator, How Do You Approach a Retrofit?

The first step is to understand the impact of your building and the opportunities to reduce its impact on the climate. Getting advice from a professional designer skilled in retrofit would be a good place to start.

It may be tempting to tackle only the “lowest hanging fruit” in a retrofit, however a “deep” retrofit should always be the aim. Retrofit works will likely interrupt normal use of the building and if only limited improvements are made, carbon emission reductions will also be limited. Completed retrofit measures will lock-in performance well into the future, so it is important to get it right the first time. Aim to go as far as you can with each step of your retrofit before moving on to the next. Retrofit should aim to maximise the feasible performance and aim for as close to new-build net zero carbon compatible performance as possible. Retrofit performance standards such as the AECB’s Building Standard or the Passivhaus Institute’s EnerPHit certification could help provide target performance levels and act as a guide to retrofit. LETI are also currently compiling Retrofit guidance.

Planning the complete retrofit in advance, rather than tackling piecemeal improvements, will help ensure that successive measures work in harmony and are implemented in a sensible order.

The retrofit hierarchy diagram shows the order in which you should approach a retrofit.

Minimising energy demands through improvements to the building’s thermal insulation, glazing, air tightness and ventilation systems should be a first step. Significant energy demand reductions can also be achieved through efficient lighting and controls, solar shading, using pumps and fans with EC direct drive motors and selecting equipment such as IT systems specifically for low energy consumption.

Reducing energy demands initially will mean that subsequent improvements like replacement of gas boilers with heat pumps will have a lower capital cost and operational energy costs will be kept as low as possible.

Finally, generating your own energy through technologies such as solar PV panels should be considered. Integration of a demand-side response (DSR) strategy with or without energy storage could further reduce energy costs, consume grid electricity at times of lowest carbon emissions and even generate income.

The challenge of ending carbon emissions is enormous and we need to accelerate the pace of change. Big UK banks and investors are setting out their environmental credentials and although legislation forcing improvements on buildings owners is currently limited, this will undoubtedly evolve. In the meantime, we need pioneering organisations, building owners and occupiers to take up the retrofit challenge and influence positive change.